This invention relates to a silver halide photographic light-sensitive material containing negative type silver halide grains each having an inner core substantially comprising silver bromide or silver iodobromide and a plurality of outer shells each provided to the outside of the inner core and substantially composed of silver bromide or silver iodobromide.
In recent years, as there have been more strict requirements for silver halide emulsions for photographic use, so have increased the demands for the high-level photographic characteristics such as a high-speed, an excellent graininess, a high sharpness, a low fog-density, a sufficiently wide exposure range and so on.
There have been the well-known high-speed emulsions such as a silver iodobromide emulsion containing silver iodide in an amount of from 0 to 10 mol % of the emulsion, to satisfy the above-mentioned requirements. About the methods of preparing the above-mentioned emulsions, there have so far been the well-known methods including, for example, an ammonia method, a neutral method, such a method as an acid method in which the conditions of pH and pAg values are controlled, and such a precipitation method as a single-jet or double-jet method.
Based upon the above-mentioned prior art and with the purposes of making the sensitivity of light-sensitive materials higher and improving the graininess thereof and, further, achieving both of the high sharpness and low fog thereof, the technical means have so far been researched with an utmost precision and have then been put into practice. A silver iodobromide emulsion which is an object of the invention have been studied so as to control not only the crystal habits and grain distribution but also the iodide content distribution in an individual silver halide grain.
For realizing the photographic characteristics including, for example, a high speed, excellent graininess, high sharpness or low fog density, the most orthodox process therefor is to improve the quantum efficiency of a silver halide used. For realizing this purpose, the observation of solid state physics and the like have positively been adopted.
There are the researches in which the above-mentioned quantum efficiency was theoretically computed and the influence on a graininess distribution was also studied. One of the researches is described in, for example, the preprints of 1980 Tokyo Symposium on Photographic Progress, titled `Interactions Between Light and Materials`, p. 91. This research predicts that a quantum efficiency could effectively be improved if a monodispersed emulsion may be prepared by narrowing a grain distribution. Further, in the so-called chemical sensitization process for sensitizing a silver halide emulsion (This process will be described in detail later.), it may be reasonably presumed that a monodispersed emulsion may also be advantageous to effectively make a light-sensitive material highly sensitive with keeping a low fog level.
For industrially preparing such a monodispersed emulsion, it is desired, as described in Japanese Patent Publication Open to Public Inspection (hereinafter called Japanese Patent O.P.I. Publication) No. 4821/1979, to apply both of the theoretically predetermined conditions of the feeding rate controls of silver ions and halide ions to be fed into a reaction system and the satisfactory conditions of the agitation thereof to the preparation process under the strict controls of the pAg and pH values of the emulsion. When a silver halide emulsion is prepared under the above-mentioned conditions, it is in either one of the cubic, octahedral and tetradecahedral crystal forms. That is to say, such an emulsion comprises the so-called normal crystal grains each having both of the (100) and (111) planes in various ratios. It is well-known that a high sensitization may be achieved by making use of the above-mentioned normal crystal grains.
Meanwhile, it has so far been well-known that the silver halide emulsions suitably used in high speed photographic films include a silver iodobromide emulsion comprising polydispersed type twinned crystal grains.
Also, silver iodobromide emulsions each containing tabular shaped twinned crystal grains are disclosed in, for example, Japanese Patent O.P.I. Publication No. 113927/1983 and others.
On the other hand, Japanese Patent O.P.I. Publication No. 22408/1978; Japanese Patent Examined Publication No. 13162/1968; `Journal of Photographic Science`, No. 24, p. 198, 1976; and the like each describe, respectively, that a development activity is increased or a high sensitization is realized by making use of multilayered type silver halide grains applied with a plurality of shells on the outside of the inner cores of the grains.
Further, West German Patent No. 2,932,650; Japanese Patent O.P.I. Publication Nos. 2417/1976, 17436/1976 and 11927/1977; and the like describe the respective silver halide grains each provided with a covering layer through a halogen substitution so as to serve as the outermost layer of the silver halide grain. These silver halide grains are practically unable to serve as any negative type emulsion, because a fixing time may be shortened thereby, however, to the contrary, a development may be thereby inhibited, so that a satisfactory sensitivity may not be obtained.
There is also well-known positive type (i.e., an internal latent image type) silver halide grains each provided outside the inner core thereof with a plurality of covering layers prepared through a halogen substitution, of which are described in, for example, U.S. Pat. Nos. 2,592,250 and 4,075,020; and Japanese Patent O.P.I. Publication No. 127549/1980. These silver halide grains are often used in an internal latent image type direct positive light-sensitive material such as those for diffusion transferring use. However, they cannot be used at all in any negative type emulsion to which the invention directed, because the internal sensitivity thereof is excessively high from the very nature of things.
There is a further silver halide grain provided on the inner core thereof with shells, as described above, and in which various iodide contents of the respective layers thereof are taken into account. This type of grains are described in, for example, Japanese Patent O.P.I. Publication Nos. 181037/1983, 35726/1985 and 116647/1984.
In the field of silver halide photographic light-sensitive materials, color light-sensitive materials each having an ISO speed of 1000 or over have recently been introduced, thanks to the various technical progress. It is, however, usual that such a light-sensitive material is deteriorated in graininess and sharpness as it becomes higher in sensitivity, and such a high speed light-sensitive material is yet very unsatisfactory for the consumers who want to admire a good photograph because its image quality is not good enough as compared with those of a conventional light-sensitive material. Therefore, a high-speed negative type light-sensitive material excellent in graininess and image sharpness has so far been demanded.
For astronomical photography, indoor photography, sport photography and the like, a further high-speed negative type light-sensitive material has particularly been demanded.